How can i copy NLA Tracks from one armature to another?
Here is Python for deep copy. Just replace the names of the source and target armatures. Hope it helps - Sri

import bpy

sourceObj = bpy.data.objects['SOURCE_ARMATURE']
targetObj = bpy.data.objects['TARGET_ARMATURE']

if targetObj.animation_data is not None:
    targetObj.animation_data_clear()

targetObj.animation_data_create()   

source_animation_data = sourceObj.animation_data
target_animation_data = targetObj.animation_data


if source_animation_data:
    for source_nla_track in source_animation_data.nla_tracks:
        target_nla_track = target_animation_data.nla_tracks.new()
        target_nla_track.name = source_nla_track.name
        for source_action_strip in source_nla_track.strips:
            target_nla_track.strips.new(source_action_strip.action.name, source_action_strip.frame_start, source_action_strip.action)